Media and multimedia provision to client over different networks have increased tremendously the last few years. Today, Internet is employed by numerous users for accessing and downloading media, e.g. in the form of video and audio streams or files, from media server. This media provision has also emerged in radio-based mobile communications networks. There is currently a very big interest in using mobile networks for multimedia or TV content. This is often referred to as Mobile-TV in the art. This media provision in the mobile networks is today mainly available through unicast transport. However, at the moment, broadcast/multicast delivery methods for Mobile-TV are under development. Examples of such standardisation efforts are 3GPP Multimedia Broadcast/Multicast Services (MBMS) and European Telecommunications Standards Institute (ETSI) Digital Video broadcasting-Handheld (DVB-H).
In line with this increasing demand for media provision in different wired and wireless communications networks, scalable media has been developed. Scalable media typically refers to coding schemes where pre-encoded bit streams can be combined, truncated or cropped to form new bit streams that target different goals, for example in terms of media quality, frame rate, screen resolution, number of transmission channels and bit rates. One paradigm is to encode once at high quality and extract multiple times to form reduced bit streams suitable for transmission in various situations. Another paradigm is to encode a first time at a low-quality and then to add additional layers that provide a quality enhancement.
The Joint Video Team (JVT) of the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T) and International Organization for Standardization/International Bectrotechnical Commission (ISO/IEC) are currently defining Scalable Video Coding (SVC) as an extension to the video codec H4.264|MPEG-4 (Moving Picture Experts Group) Advanced Video Coding (AVC). SVC provides full scalability in three dimensions; temporal, spatial and signal-to-noise ratio (SNR), and is expected to become an international standard shortly. MPEG is also currently exploring scalable audio and speech coding.
However, the current management of scalable media streams in streaming or downloading servers is mainly concerned with the storage of one or more scalable media streams and extraction of data from this stream. No special considerations are made to optimize the bandwidth usage for the simultaneous extraction of data streams.